The present invention relates to a device for analyzing the activity of a radioactive aerosol as a function of the grain size distribution of its particles.
This analyzer is more particularly suited to the rapid evaluation of the activity of inhalable particles suspended in the air of a room or the like which is liable to be contaminated. Thus, the penetration of the human organism via the respiratory tracts of the different constituent particles of an aerosol is a direct function of their grain size distribution. For this reason it is very useful to establish the spectrum of their activity as a function of their grain size in order to evaluate the contamination risk involved.
In order to analyze the activity of a radioactive aerosol as a function of the grain size distribution of its particles it is necessary to successively separate the aerosol particles into particle batches of a given grain size and to determine the activity of each of the particle batches.
It is conventional practice to use a device called a "cascade impacter" for separating the particles of an aerosol into particle batches of a given grain size. Within a tight enclosure such an impacter has a plurality of stages, each of which collects particles of a given grain size when an aerosol is put into operation in the enclosure, whereby each stage has an aerosol injection plate perforated by at least one calibrated opening and a particle collection plate. However, these "impacters" do not permit the direct measurement of the activity of the particles of one stage without manual intervention within the latter.
Thus, prior to the present invention it was necessary to dismantle the collection plate of one stage in order to measure, e.g. by means of a photomultiplier the radioactive activity of particles collected in said stage.
Thus, prior to the present invention it was not possible to carry out in complete safety and with adequate accuracy the analysis of the activity of a radioactive aerosol as a function of the grain size distribution of its particles.